This is a request for a supplement for the training grant ?Training in Molecular Toxicology? at UCLA that was not funded in the last review. We request continuing support for four graduate students for the upcoming year to ensure that they can continue their training. The two current postdoctoral trainees are moving on with their careers and we are therefore not requesting continued support for them. The number of training grant faculty remains at 14, but 4 of the faculty are new. As a result, the number of female T32 faculty has increased from 4 to 6, and more junior faculty are involved. The faculty come from 12 different departments in five different schools at UCLA, reflecting the interdisciplinary nature of our molecular toxicology training program. Seven faculty have M.D. degrees. These faculty provide a potential avenue for the recruitment of physician scientists to the training grant, and provide a translational perspective to our trainees. Our NIEHS T32 is relatively unique in having a particular focus on the mechanisms whereby environmental toxicants cause disease. The faculty have five major foci of research interest i) the role of pesticides in the etiology of Parkinson?s disease, (ii) the toxic effects of secondhand and third-hand cigarette smoke and of fossil fuels and their combustion products, iii) epigenetic effects of endocrine disruptors and other toxicants, iv) heavy metal toxicity, and v) nanotoxicology. These research foci are highly relevant to environmental challenges confronting California and the nation. A major feature of our research is the use of common and alternative model organisms to provide insights into toxicological processes. UCLA has committed considerable resources to the molecular toxicology program. Very importantly, a search (chaired by the PI of this T32) is underway for a state-funded tenure-track faculty position in the area of the molecular toxicology of disease. The UCLA Academic Senate undertook an eight year review of the Molecular Toxicology IDP in 2018. The resulting report was highly supportive of the program. Our faculty have substantial NIEHS and non-NIEHS funding. We had great success in recruiting excellent predoctoral and postdoctoral trainees, and we have been successful in URM student and postdoc recruitment. Our trainees have excellent publication records in high impact journals. Our past trainees have successfully transitioned into important positions in academia, government or industry. The training grant has catalyzed the expansion and consolidation of molecular toxicological research and training at UCLA, and has stimulated interactions and collaborations among the participating faculty and their trainees. Continuation of support for our students should encourage more students and postdocs to pursue research in toxicology, and will signal the increasing importance of toxicology at UCLA.